Comments on "Efficient deadlock prevention policy in automated manufacturing systems using exhausted resources"

As reported by Hu and Li (International Journal of Advanced Manufacturing Technology 40:566-571, 2009), in order to design liveness-enforcing supervisors for automated manufacturing systems (AMS), a deadlock prevention policy was proposed based on the exhausted resources. The proposed policy exploits a special structure of Petri nets for the liveness of a specific system. In order to show the applicability of this method, two examples were considered. One of the examples involves an AMS with a large-state space. Unfortunately, the liveness-enforcing supervisor containing seven monitors (control places) computed as reported by Hu and Li (International Journal of Advanced Manufacturing Technology 40:566-571, 2009) to enforce liveness on this system does not provide a live behaviour. This paper reports this fact.